scholarly journals A New Model for Predicting Dynamic Surge Pressure in Gas and Drilling Mud Two-Phase Flow during Tripping Operations

2014 ◽  
Vol 2014 ◽  
pp. 1-16 ◽  
Author(s):  
Xiangwei Kong ◽  
Yuanhua Lin ◽  
Yijie Qiu ◽  
Hongjun Zhu ◽  
Long Dong ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Drill Pipe ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Operating Speed ◽  
Drilling Mud ◽  
Two Phase ◽  
Influx Rate ◽  
Conservation Equations ◽  
Calculation Results

Investigation of surge pressure is of great significance to the circulation loss problem caused by unsteady operations in management pressure drilling (MPD) operations. With full consideration of the important factors such as wave velocity, gas influx rate, pressure, temperature, and well depth, a new surge pressure model has been proposed based on the mass conservation equations and the momentum conservation equations during MPD operations. The finite-difference method, the Newton-Raphson iterative method, and the fourth-order explicit Runge-Kutta method (R-K4) are adopted to solve the model. Calculation results indicate that the surge pressure has different values with respect to different drill pipe tripping speeds and well parameters. In general, the surge pressure tends to increase with the increases of drill pipe operating speed and with the decrease of gas influx rate and wellbore diameter. When the gas influx occurs, the surge pressure is weakened obviously. The surge pressure can cause a significant lag time if the gas influx occurs at bottomhole, and it is mainly affected by pressure wave velocity. The maximum surge pressure may occur before drill pipe reaches bottomhole, and the surge pressure is mainly affected by drill pipe operating speed and gas influx rate.

Establishment and Solution of the RNC Flow Network Model

2014 ◽  
Vol 548-549 ◽  
pp. 1783-1789
Author(s):  
Li Ying Sun ◽  
Lu Jie Zhen ◽  
Yi Tong Li
Keyword(s):  
Network Model ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Two Phase ◽  
Conservation Equations ◽  
Flow Network ◽  
Cycle System ◽  
Variable Step ◽  
The Mathematical Model

The mathematical model based on graph theory and the refrigerant natural cycle system of gas-liquid two-phase flow network is established. Incidence matrix was used to describe the relationships between the various components. The node conservation equations, branch equations, momentum conservation equation in return circuit and mass conservation equations of system are established. The model was solved by using variable step gird iterative method. Then refrigerant state of each node and refrigerant flow of each branch in network model are obtained. Establishment and solution of the RNC network model provides an effective way for the further performance analysis of system.

Modeling of Sand Cleanout With Foam Fluid for Vertical Well

SPE Journal ◽  
2010 ◽  
Vol 15 (03) ◽  
pp. 805-811 ◽  
Author(s):  
Songyan Li ◽  
Zhaomin Li ◽  
Riyi Lin ◽  
Binfei Li
Keyword(s):  
Mathematical Model ◽  
Volume Flow Rate ◽  
Injection Pressure ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Foam Density ◽  
Conservation Equations ◽  
Calculation Results ◽  
The Mathematical Model ◽  
Oil Formation

Summary Foam has proved to be effective and economical in underbalanced operations and is gaining wider applications in many areas. Foam fluid has low density and high blocking ability. It can effectively reduce leaking of fluid into formation in low-pressure wells, protecting the oil formation and improving sand-cleanout efficiency. According to energy-conservation equations, mass-conservation equations, and momentum-conservation equations, a mathematical model for sand cleanout with foam fluid was established that considers the heat transfer between foam in the annulus and foam in the tubing. The model was solved by numerical method. Distributions of foam temperature, foam density, foam quality, pressure, and foam velocity in the wellbore were obtained. Calculation results show that temperature distribution is affected greatly by thermal gradient. As the well depth increases, foam pressure and foam density increase and foam quality and velocity decrease. Foam velocity at the well bottomhole is the minimum. Friction pressure loss of foam is less than that of water at the same volume flow rate. Site applications show that sand cleanout with foam fluid can prevent fluid leakage effectively. It can avoid damage of sealing agents and reduce pollution. The average relative error and standard deviation between model and field data on injection pressure are–0.43 and 2.55%, respectively, which proves the validation of the mathematical model.

scholarly journals Calculation Analysis of Pressure Wave Velocity in Gas and Drilling Mud Two-Phase Fluid in Annulus during Drilling Operations

2013 ◽  
Vol 2013 ◽  
pp. 1-17 ◽  
Author(s):  
Yuanhua Lin ◽  
Xiangwei Kong ◽  
Yijie Qiu ◽  
Qiji Yuan
Keyword(s):  
Wave Velocity ◽  
Void Fraction ◽  
Pressure Wave ◽  
Angular Frequency ◽  
Mass Force ◽  
Virtual Mass ◽  
Drilling Mud ◽  
Influx Rate ◽  
Drilling Operations ◽  
Well Depth

Investigation of propagation characteristics of a pressure wave is of great significance to the solution of the transient pressure problem caused by unsteady operations during management pressure drilling operations. With consideration of the important factors such as virtual mass force, drag force, angular frequency, gas influx rate, pressure, temperature, and well depth, a united wave velocity model has been proposed based on pressure gradient equations in drilling operations, gas-liquid two-fluid model, the gas-drilling mud equations of state, and small perturbation theory. Solved by adopting the Runge-Kutta method, calculation results indicate that the wave velocity and void fraction have different values with respect to well depth. In the annulus, the drop of pressure causes an increase in void fraction along the flow direction. The void fraction increases first slightly and then sharply; correspondingly the wave velocity first gradually decreases and then slightly increases. In general, the wave velocity tends to increase with the increase in back pressure and the decrease of gas influx rate and angular frequency, significantly in low range. Taking the virtual mass force into account, the dispersion characteristic of the pressure wave weakens obviously, especially at the position close to the wellhead.

scholarly journals Lattice Boltzmann Simulation of Ferrofluids Film Boiling

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 881
Author(s):  
Mohammad Yaghoub Abdollahzadeh Jamalabadi
Keyword(s):  
Magnetic Field ◽  
Nusselt Number ◽  
Lattice Boltzmann ◽  
Mass Conservation ◽  
Vapour Phase ◽  
Momentum Conservation ◽  
Film Boiling ◽  
Parameter Study ◽  
Two Phase ◽  
Lattice Boltzmann Simulation

In the present investigation, two phase film boiling of ferrofluids under an external field delivered around a two-dimensional square cross-section heater was investigated using the lattice Boltzmann technique. The purpose of this work is to find the effect of magnetic field magnitude and direction on the Nusselt number in single and double heater geometry. The improving thermal efficiency in the horizontal and vertical placement of heaters is also presented. The governing equations of mass conservation, momentum conservation, and energy conservation are solved by using a central-moments-based Lattice Boltzmann scheme. The air pocket generated around heater raised incorporating magnetic effects. The heat transfer through this advancement has been explored quantitatively and abstractly. The results shows that with the development in the volumetric applied force at the bubble-fluid interface, the bubble boundary layer thickness around the square heater lessened which cause the Nusselt number augmented. Through the parameter study it found that the Nusselt number can be essentially extended by altering the course of magnet shafts, and that film rising outwardly of the bubble. The improvement and advancement of vapour phase in various heater arrangement made two column of bubble rises at the same time, which rose above each heater and in the end changed into one column of bubble. A correlation considering magnitude and angle of the magnetic field on time-averaged Nusselt number is presented. Finally, the Nusselt number can be controlled with the help of the incorporation of other heaters.

scholarly journals A Novel Dynamic Model for Predicting Pressure Wave Velocity in Four-Phase Fluid Flowing along the Drilling Annulus

2015 ◽  
Vol 2015 ◽  
pp. 1-17 ◽  
Author(s):  
Xiangwei Kong ◽  
Yuanhua Lin ◽  
Yijie Qiu ◽  
Xing Qi
Keyword(s):  
Dynamic Model ◽  
Wave Velocity ◽  
Pressure Wave ◽  
Drilling Fluid ◽  
Dynamic Pressure ◽  
Mass Force ◽  
Virtual Mass ◽  
Influx Rate ◽  
Calculation Results ◽  
Phase Fluid

A dynamic pressure wave velocity model is presented based on momentum equation, mass-balance equation, equation of state, and small perturbation theory. Simultaneously, the drift model was used to analyze the flow characteristics of oil, gas, water, and drilling fluid multiphase flow. In addition, the dynamic model considers the gas dissolution, virtual mass force, drag force, and relative motion of the interphase as well. Finite difference and Newton-Raphson iterative are introduced to the numerical simulation of the dynamic model. The calculation results indicate that the wave velocity is more sensitive to the increase of gas influx rate than the increase of oil/water influx rate. Wave velocity decreases significantly with the increase of gas influx. Influenced by the pressure drop of four-phase fluid flowing along the annulus, wave velocity tends to increase with respect to well depth, contrary to the gradual reduction of gas void fraction at different depths with the increase of backpressure (BP). Analysis also found that the growth of angular frequency will lead to an increase of wave velocity at low range. Comparison with the calculation results without considering virtual mass force demonstrates that the calculated wave velocity is relatively bigger by using the presented model.

Numerical Simulation of Low-Current Vacuum Arc Plasma

2011 ◽  
Vol 383-390 ◽  
pp. 4843-4847
Author(s):  
Peng Sun ◽  
Rong Ni Yan
Keyword(s):  
Fluid Model ◽  
Mass Conservation ◽  
Momentum Conservation ◽  
Conservation Equation ◽  
Vacuum Arc ◽  
Symmetric Model ◽  
Ion Temperature ◽  
Plasma Parameters ◽  
Conservation Equations ◽  
Mhd Model

Three-dimensional magnetohydrodynamic(MHD) model of vacuum arc was built based on two-fluid model of ion and electron and Maxwell equation. In the MHD model mass conservation equation, momentum conservation equations, energy conservation equations of ion and electron, electric potential equations and magnetic equations were considered. With the aid of Computational Fluid Dynamics(CFD) software FLUENT and Re-development by visual C++, the important plasma parameters of low current vacuum arc , such as axial current density , ion temperature, electron temperature, mach number, were analyzed. The simulation results shown that the distribution of plasma parameters is consistent with that of the 2D axis-symmetric model.

scholarly journals The space-time conservation element and solution element scheme for simulating two-phase flow in pipes

2019 ◽  
Vol 11 (12) ◽  
pp. 168781401989835 ◽  
Author(s):  
Rana Danish Aslam ◽  
Ashiq Ali ◽  
Asad Rehman ◽  
Shamsul Qamar
Keyword(s):  
Source Term ◽  
Two Phase Flow ◽  
Mass Conservation ◽  
Space Time ◽  
Upwind Scheme ◽  
Phase Flow ◽  
Two Phase ◽  
Conservation Equations ◽  
Element Scheme ◽  
Solution Element

In this article, the space-time conservation element and solution element scheme is extended to simulate the unsteady compressible two-phase flow in pipes. The model is non-conservative and the governing equations consist of three equations, namely, two mass conservation equations for each phase and one mixture-momentum equation. In the third equation, the non-conservative source term appears, which describes the sum of gravitational and frictional forces. The presence of source term and two mass conservation equations in considered model offers difficulties in developing the accurate and robust numerical techniques. The suggested space-time conservation element and solution element numerical scheme resolves the volume-contact discontinuities efficiently. Furthermore, the modified central upwind scheme is also extended to solve the same two-phase flow model. The number of test problems is considered, and the results obtained by space-time conservation element and solution element scheme are compared with the solutions of modified central upwind scheme. The numerical results show better performance of the space-time conservation element and solution element method as compare to the modified central upwind scheme.

Thermal-Hydraulics of OC-OTEC Spout Flash Evaporators

1992 ◽  
Vol 114 (3) ◽  
pp. 187-196 ◽  
Author(s):  
S. M. Ghiaasiaan
Keyword(s):  
Size Distribution ◽  
Droplet Size ◽  
Two Phase Flow ◽  
Mechanistic Model ◽  
Droplet Size Distribution ◽  
Momentum Conservation ◽  
Phase Flow ◽  
Two Phase ◽  
Conservation Equations ◽  
Size Groups

A mechanistic model was developed for the thermal-hydraulic processes in the spout flash evaporator of an OC-OTEC plant. Nonequilibrium, two-fluid, conservation equations were solved for the two-phase flow in the spout, accounting for evaporation at the gas-liquid interface, and using a two-phase flow regime map consisting of bubbly, churn-turbulent and dispersed droplet flow patterns. Solution of the two-phase conservation equations provided the flow conditions at the spout exit, which were used in modeling the fluid mechanics and heat transfer in the evaporator, where the liquid was assumed to shatter into a spray with a log-normal size distribution. Droplet size distribution was approximated by using 30 discrete droplet size groups. Droplet momentum conservation equations were numerically solved to obtain the residence time of various droplet size groups in the evaporator. Evaporative cooling of droplets was modeled by solving the 1-D heat conduction equation in spheres, and accounting for droplet internal circulation by an empirical thermal diffusivity multiplier. The model was shown to favorably predict the available single-spout experimental data.

CFD-Calculation of the Flashing Flow in Pipes and Nozzles

2002 ◽  
Author(s):  
S. Maksic ◽  
D. Mewes
Keyword(s):  
Vapor Phase ◽  
Nuclear Reactor ◽  
Three Dimensional ◽  
Mass Conservation ◽  
Vapour Phase ◽  
System Of Equations ◽  
Two Phase ◽  
Model Calculations ◽  
Conservation Equations ◽  
Flow Through

Within the framework of the nuclear reactor safety analysis of pressurised water reactor the flashing flow in pipes and nozzles is examined using a CFD numerical calculation. For the calculation of transient flashing flow a three dimensional CFD model is developed with the aim to predict the propagation of the pressure waves in the two phase flow through the three dimensional geometry. As the most important factor for the modelling of flashing flow, the thermal non-equilibrium between the phases is taken into account. The generation and the propagation of the vapor phase are modelled by conservation equations for the bubble number density according to the model of Jones [1] and mass conservation equations for the vapour phase. The turbulence of the flow is described with the k-ε model. The influence of the dispersed vapor phase on the turbulence is neglected. The system of equations is implemented into the commercial CFD-code CFX4.2. The solution of the system of equations is done numerically with the method of finite volumes. For the verification of the model, calculations of the flow through a converging-diverging nozzle are carried out and the results are compared with experimental ones [2].

scholarly journals Study of the Effect of Centrifugal Force on Rotor Blade Icing Process

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Zhengzhi Wang ◽  
Chunling Zhu
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Force ◽  
Rotor Blade ◽  
Flow Direction ◽  
Three Dimensional ◽  
Simulation Method ◽  
Two Phase ◽  
Numerical Simulation Method ◽  
Calculation Results ◽  
Flow Field Characteristics

In view of the rotor icing problems, the influence of centrifugal force on rotor blade icing is investigated. A numerical simulation method of three-dimensional rotor blade icing is presented. Body-fitted grids around the rotor blade are generated using overlapping grid technology and rotor flow field characteristics are obtained by solving N-S equations. According to Eulerian two-phase flow, the droplet trajectories are calculated and droplet impingement characteristics are obtained. The mass and energy conservation equations of ice accretion model are established and a new calculation method of runback water mass based on shear stress and centrifugal force is proposed to simulate water flow and ice shape. The calculation results are compared with available experimental results in order to verify the correctness of the numerical simulation method. The influence of centrifugal force on rotor icing is calculated. The results show that the flow direction and distribution of liquid water on rotor surfaces change under the action of centrifugal force, which lead to the increasing of icing at the stagnation point and the decreasing of icing on both frozen limitations.

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